Supreme Court decision uses controversial rationale

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WASHINGTON — The Supreme Court declared the execution of anyone under the age of 18 to be unconstitutional on Tuesday, effectively ending a practice used in 19 states. NBC's Justice Correspondent, Pete Williams, explains the implications of the ruling.

What was the rationale for the court's decision?

Pete Williams: The court analyzed the question of whether it is constitutional to execute offenders who were 16 or 17 when they committed their crimes, under the Eighth Amendment, which bars cruel and unusual punishment.

What the court said it had to do is see if there is "an emerging national consensus" on the question and it concluded there is.

Some of this is mathematical. The court says that of the states that still had the juvenile death penalty, five of them in the past 15 years have decided to ban it, through legislation or court decision. In the rest of the states, the number of juvenile executions has dropped.

The second reason the court cited is the scientific evidence.

The court said there is widespread agreement among mental health experts that people under the age of 18, in general, are less morally responsible for their crimes: their minds are less well developed, they're more susceptible to peer pressure and they're less culpable, morally, for what they do. The court said there is less evidence that people under 18 are irretrievably immoral. And the decision says, there's a greater possibility for these people to improve their characters.

Finally, the court said — and I think this is a very controversial part of the decision, sure to be widely debated — if you look around at what the rest of the world is doing, the United States is the only country left that still executes offenders who were 16 and 17 when they committed murderers.

It said look at the number of countries who, within the past five to ten years have moved away from it — Iran, Pakistan, Saudi Arabia and the Congo. America is one of the only ones left. And therefore, the Supreme Court says the international community has moved away from it as well. The court said that's also a reason the death penalty should be struck down for juvenile offenders.

It was a close decision. What was the minority point of view?
In the 5-4 decision, the dissent was very spirited. Justice Antonin Scalia, writing for the four dissenters — Scalia, Sandra Day O'Conner, Clarence Thomas, and Chief Justice William Rehnquist — said the court's math is all wrong. The reason states don't execute as many juveniles now, Scalia said, is that juries are capable of taking youth into account.

Justice Scalia bitterly denounced the majority's reliance on international law. He says it is entirely inappropriate for the Supreme Court to look at what the rest of the world is doing, because the Supreme Court doesn't do that all the time. The court, he says, just picks and chooses times when it wants to look at international consensus. It doesn't do it on abortion, he says.

He thinks that is not the way for the United States Supreme Court to interpret the U.S. Constitution.

What are the implications of the decision?
This will affect about 73 juvenile offenders who are currently on death row and it means from now on, no state may seek the death penalty for an offender who was 16 or 17 when the crime was committed.

Incidentally, it was 15 years ago when the United States Supreme Court said the death penalty is unconstitutional for anyone under 16. This decision dealt only with 17 or 18 year olds.

Pete Williams is NBC News' Justice Correspondent and is based in Washington, D.C.